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Re: [PATCH 0/4] dm verity: add support for error correction

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On Mon, 9 Nov 2015, Sami Tolvanen wrote:

> > Also, the 2 other big questions from Mikulas need answering:
> > 1) why aren't you actually adjustng error codes, returning success, if
> >    dm-verity was able to trap/correct the corruption?
> 
> We don't see actual I/O errors very often. Most corruption we've seen
> is caused by flaky hardware that doesn't return errors. However, I can
> certainly change to code to attempt recovery in this case too.

What flash controller and chips do you use? What is the probability of I/O 
error and what is the probability of silent data corruption? Is the silent 
data corruption permanent or transient? What is causing the silent data 
corruption (decay in flash chips?, errors on the bus?) Why can't you ask 
the hardware engineers to use a controler with proper error correction?

Without these data - it looks like you first wrote the patch and then 
tried to make some excuses why it should be accepted.

I'm also a little bit concerned that the patch will increase prevalence of 
crapware on the market - when accepted, this kind of reasoning will 
follow: "now we have error correction in the kernel, so we cut down flash 
overprovisioning, save a dollar or two per device, and produce a crap that 
randomly corrupts user's data on the read-write partition (because that 
partition not protected by the error correction)".

Mikulas
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[PATCH 0/4] dm verity: add support for error correction Sami Tolvanen <samitolvanen@google.com> - 2015-11-05 03:10 +0100
  [PATCH 1/4] dm verity: clean up duplicate hashing code Sami Tolvanen <samitolvanen@google.com> - 2015-11-05 03:10 +0100
  [PATCH 4/4] dm verity: ignore zero blocks Sami Tolvanen <samitolvanen@google.com> - 2015-11-05 03:10 +0100
  [PATCH 3/4] dm verity: add support for forward error correction Sami Tolvanen <samitolvanen@google.com> - 2015-11-05 03:10 +0100
    Re: [PATCH 3/4] dm verity: add support for forward error correction kbuild test robot <lkp@intel.com> - 2015-11-05 06:40 +0100
  [PATCH 2/4] dm verity: separate function for parsing opt args Sami Tolvanen <samitolvanen@google.com> - 2015-11-05 03:10 +0100
  Re: [PATCH 0/4] dm verity: add support for error correction Milan Broz <mbroz@redhat.com> - 2015-11-05 08:40 +0100
    Re: [PATCH 0/4] dm verity: add support for error correction Sami Tolvanen <samitolvanen@google.com> - 2015-11-05 18:40 +0100
      Re: [PATCH 0/4] dm verity: add support for error correction Mike Snitzer <snitzer@redhat.com> - 2015-11-09 17:40 +0100
        Re: [PATCH 0/4] dm verity: add support for error correction Sami Tolvanen <samitolvanen@google.com> - 2015-11-09 20:20 +0100
          Re: [PATCH 0/4] dm verity: add support for error correction Mike Snitzer <snitzer@redhat.com> - 2015-11-09 21:00 +0100
          Re: [PATCH 0/4] dm verity: add support for error correction Milan Broz <mbroz@redhat.com> - 2015-11-12 11:40 +0100
          Re: [PATCH 0/4] dm verity: add support for error correction Mikulas Patocka <mpatocka@redhat.com> - 2015-11-12 20:00 +0100
    Re: [PATCH 0/4] dm verity: add support for error correction Mikulas Patocka <mpatocka@redhat.com> - 2015-11-06 18:30 +0100
      Re: [PATCH 0/4] dm verity: add support for error correction Sami Tolvanen <samitolvanen@google.com> - 2015-11-06 20:10 +0100
        Re: [dm-devel] [PATCH 0/4] dm verity: add support for error  correction Zdenek Kabelac <zkabelac@redhat.com> - 2015-11-06 20:30 +0100
          Re: [dm-devel] [PATCH 0/4] dm verity: add support for error  correction Sami Tolvanen <samitolvanen@google.com> - 2015-11-06 21:30 +0100
            Re: [dm-devel] [PATCH 0/4] dm verity: add support for error  correction Zdenek Kabelac <zkabelac@redhat.com> - 2015-11-06 22:10 +0100
              Re: [dm-devel] [PATCH 0/4] dm verity: add support for error  correction Sami Tolvanen <samitolvanen@google.com> - 2015-11-06 22:30 +0100
                Re: [dm-devel] [PATCH 0/4] dm verity: add support for error  correction Mikulas Patocka <mpatocka@redhat.com> - 2015-11-07 16:30 +0100
            Re: [dm-devel] [PATCH 0/4] dm verity: add support for error  correction Mikulas Patocka <mpatocka@redhat.com> - 2015-11-07 16:30 +0100
        Re: [PATCH 0/4] dm verity: add support for error correction Mikulas Patocka <mpatocka@redhat.com> - 2015-11-07 16:20 +0100
          Re: [PATCH 0/4] dm verity: add support for error correction Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-11-09 16:10 +0100

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